Saturday, March 19, 2016
There was a quake yesterday at the north end of the Pacific Subduction Zone, and another one two weeks ago. In looking over my list of quakes over the last year, nearly all of them were either at the north end by Vancouver Island, and the south end by Ferndale, California. This worries me a little. The center part of the Zone appears to be locked. Here is a plot of quakes over the last 40 years or so that confirms my impression:
Thus the northern and southern ends seem to be moving, but the center part looks like it is storing up a possibly tremendous amount of energy. In my list over the last year just two of the magnitude 5+ quakes have occurred off of the Oregon Coast. But the plate north of that seems to have none. I've reported an average of one quake on the Subduction Zone about once a month which I felt reassured me that energy is being dissipated a little at a time, but now I'm not so reassured about big one being far off.